Most actors prepare witty anecdotes to share while appearing on talk shows, but Kristen Bell threw out the script in a recent interview and took us to an entirely new, and pretty gross, place.

Appearing on The Joel McHale Show this week, the 37-year-old revealed that she'd recently recovered from a severely contagious case of "anal worms".

"I'm not here to talk about pinworms, but I will," The Good Place star told host Joel McHale in an impromptu health lesson.

"50 percent of people over 15 don't experience symptoms, which is the itch," she explained.

According to the mum of two, "Your kids get them because they put their hands in their mouth, and they lay eggs."

After noticing there were suddenly no carpets in her three-year-old daughter Delta's preschool, Bell found out that there was a "pinworm problem" at the school, and immediately went into mum mode.

"Of course I immediately Googled it, and it’s like so, so contagious," she said, vividly describing her first worm sighting while examining her child's poo.

"You have to monitor, and you have to look in their poop. And when you wipe their butt, sure enough — I wiped, and saw a little white worm. I know, she’s really gross. My daughter, not the worm. The worm was gross, too."

Later that day, Bell says she discovered that she too was infected with worms and said that while it's not painful, the condition is "very itchy".

She then made her whole family, including husband Dax Shepard, take medication, although the actor believes only she and Delta were lucky enough to play host to the pesky parasites.